area has also been approved and has been coordinated with the agency which has been using the Range." The XW-25 warhead was flown to the airstrip at Yucca Flat, then trucked to Watertown.
It was stored in Building 10 prior to being moved to Area 13 for final placement.
The Project 57 shot was originally scheduled for early April, but was pushed back several times. Personnel at Watertown were undoubtedly evacuated before the shot in case of unfavorable winds that could spread plutonium over the airbase, or an unexpected nuclear yield. Evacuation must have been terribly inconvenient to flight test and training operations at Watertown. According to declassified documents, most of the delays were due to unfavorable weather conditions.
Finally, on the morning of 24 April, the signal was sent to the detonator, and the warhead's high explosive charge destroyed the weapon. Although there had been no obvious atomic explosion, a three-man team in protective clothing was dispatched to determine whether or not any beta or gamma radiation hazard existed from a partial nuclear yield.
There was none, but all personnel entering the area were required to wear full protective suits and respirators to shield themselves from alpha radiation emitted by plutonium.
This Russian satellite image shows Area 51 and Area 13. Groom Lake is about three miles long from north to south. Ground Zero for the Project 57 plutonium dispersal test was located five miles northwest of the edge of Groom Lake.
Several isotopes of plutonium (Pu) are typically found at safety experiment sites: Pu-238 (with a half-life of 89 years), Pu-239 (24,300 years), Pu-240 (6,600 years), and Pu-241 (14 years). Pu-239 is the most abundant. The decay of Pu-241 produces an americium isotope, Am-241, which emits gamma rays and has a half-life of 432 years.
Radiation Safety (Rad-Safe) technicians measure gamma emissions from Am-241 with a device called a FIDLER (Field Instrument for the Determination of Low-Energy Radiation). Am-241 activity in contaminated soil provides a reasonable indication of Pu-239/240 levels.
Plutonium emits alpha particles, the weakest form of radiation. A sheet of paper is sufficient shielding against alpha radiation. Although alpha particles are highly energetic, they are not